Telephone-exchange system.



E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG. 1I 1 906,

9 SHBETSQSHEET 1.

' E. E CLEMENT. TELEPHONE EXCHANGE SYSTEM. APPQl- ICATIONTILED AUG. 1,1906.

Patented Aug. 11,1914

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APPLICATION FILED AUG.1, 1906.

Patented Augull, 1914.

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B. E. CLEMENT. TELEPHONE EXGHANGE SYSTEM APPLICATION FILED AUG. 1, 1906.

- Patented Aug. 11,1914.

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CLEMENT. TELEPHONE EXCHANGE SYSTEM.

APPLICATION? FILED AUG l, 1906.

lwenioz E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM. {.FPLIGATION FILED AUGPatented-Aug. 11, 191

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E. E GLEMENTJ TELEPHONE EXCHANGE SYSTEM.

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Patented mg. 11, 1914,

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TELEPHONE EXCHANGE SYSTEM. APPLIGATIONTILED AUGJ, 1906 1,107,148. IPatented Aug.11,1914.

9 SHEETSSHBET 9- witnesses UNITED STATES PATENT orrron.

nnwann n. CLEMENT, or WASHINGTON, DISTRICT. or COLUMBIA, ASSIGNOR, BY

MESNE ASSIGNMENTS, To FREDERICK c. STEVENS, or a'TTIcA, N W YORK.

TELEPHONE EXQHANGE SYSTEM.

have invented certain new and useful Improvements in Telephone-ExchangeSystems, of which the following is a specification, reference being hadtherein to the accompanying drawing. 4 r

My invention relates to telephone ex change systems and has for ,itsobject the production of such a syste "in which the calls originating atsubserib rs stations are distributed among connective terminals such asoperators plugs, in an improved manner.

Briefly stated, my invention comprises connective apparatus, which maybe either manual erautomatic as regards the calling part thereof, andwhich is provided with what I have called relay primary selectors, asdescribed in the above mentioned applica- 'tion, for the purpose ofanswering incoming calls and connecting the calling lines to idle trunksor connective circuits. These relays are arranged so that they bear adecimal relation to each other and to the lines, and they are positivein their action, being controlled by the calling lines themselves.

In'operation,when a line calls, its line relay pulls up,-closing thecircuit of the appropriate tens and units relays of that hundrcds groupto which the calling line helongs, and these two relays in pulling upconnect the line onto the trunk with which they are associated. Suchconnection being complete, the conditions are the same as if an operatorhad manually inserted a plug into the ordinary answering'jackof thecalling line; and the sleeve or other relays of the trunk, as well asthe cut-ofi' relay of the line, immediately take current and performtheir usual functions. The primary selector relays are self-locking, andthe locking circuit for each trunk group is controlled by one of thedistinctive trunk relays which responds to acts of the subscriber,whereby at the conclusion of the"COI'IYQI'SiLllOll, when the subscriberhangs ,up his receiver, the locking circuit is broken and the primaryselector relays let go, discoi'lnecting the line from the trunk in thesame manner as if an operator had pulled out an answering plug which hadpreviously been inserted.

In. the present application I have specifically illustrated, "and shallhereinafter spe- Specification. of Letters Patent.

Patented Aug. 11, 1914.

Application filed August 1, 1906. Serial N 0. 328,723.

matic switch circuits, the trunks themselves being controlled byoperators, who manipulate the automatic switches in order to effectconnect-ion with the wanted lines as they are called for. In order toenable the operators to conveniently control the switches I provide eachoperator with a'plurality of push button keys somewhat similar to thoseused in computing machines, these keys serving to connect a power drivenimpulse trans- I cifically describe and claim, primary selector relaysapplied to trunks leading into auto-f mitter or transmitters to therespective trunks as they come into use and according to the numberswanted.

This description is accompanied by figures, in Which Figure 1 showssubstation telephone equipments; Figs. 2, 3 and 4 show relays involvedin a system of automatic call distribution; Fig. 5 shows manualconnectin units; Fig. 6 shows a selective impulse sen ing device; Fig. 7shows an automatic switch or connector; Fig. 8 shows the scheme of theconnecting relays of Figs. 2, 3 and ten and Figs. 9 and 10 show detailof a relay having a large number ofcontacts. Figs. 1

to 7 may be arranged to' form one large diagram of the system of myinvention.

That portion of my system which is illus-.

trated' in Figs. 2, 3 and 4 constitutes what I' have termed the primaryselector or answering portion of the system. I1 this, as already setforth, appear a nu. ber of ten point relays and a number of single pointor ordinary relays. These latter may be of any suitable type. The onlyspecial feature required is that of double winding, which, as I shallpoint out hereinafter, can be dispensed with if some other means beprovided for locking the relays when energized. The apparatus at thesubscribers stations also forms no part in itself of my presentinvenlion, except as it co-acts with the apparatus. and circuits at thecentral office. I contemplate usiug an ordinary common battery telephoneoutfitthe same as those employed in standard manual switchboard systems.

Referring then to Figs. 9 and 10, I will briefly describe the ten p'ointrelay, N. This comprises an iron back yoke, n, a pair of magnets, a,mounted thereon, an armature, n extending across the front end thereof,and a set of contact-springs, a n n n overlying the upper bell-crankextension of back yoke, n. Upon this return portion, a,

' ot the front yoke the upper bell-crank arm,

bcginning .with Fig. 1. showirtlnre subscribers stations, ilk,- ir. A

n, of the armature, "n. lies fiat under normal conditions. Cut from endto end of this upper bell-crank portion, n, are two grooves in whichrest the insulating studs of the spring sets. The function of theseslots with the studs resting in them is to retain the armature in place.At their front ends the springs are separated by shouldered studs, thelowermost stud of each pair resting upon the armature, carrying'thelower spring of its pair, 72., on its shoulder, and the upper spring, a,on its head, its stem passing through a. hole in the spring, it, whilethe mapermost stud of each pair rests upon the spring, 'n supports thespring, it, upon its shoulder, and carries the spring, at, on its head,its stem passing through a hole in the spring, at. The actuating studs all'ect only the springs, n, if of each set, those constituting themovable springs, while the others, n a are fixed. Each actuatingv studcarries the spring, n, on its shoulder, and the spring, at, on its head,ils stem passing through holes in the springs, a n. The entire relay issecured to an insulating hack block, 11. by means of the bolts, n,

constituting extensions ot the cores and threaded to receive look-nuts.The rear ends of the COIlttlClI-SIHITIQ'S extend out through openingsmade in this block, and an inclosing shell or casing, 02. is titted tothe block. with which it forms'a tight joint all around the edge. Thisshell is secured in place by means of the stud, n, threaded to receivethe nuts, 12.. As the armature. n is attracted, the springs. n", n, arelifted by the actuating stud, until their outer points make contact withthe corresponding points of the springs, n, it, in each set. T a1 ofthese sets are line-contacts, and the eleventh is for locking purposes.as will sullicicntly appear 'trom the description of the circuits.

Following is a description of the circuits, Tl'icrciu I have V 7 eachequipped with a telephone trai'ismittcr, a receiver. switch hook, aringer, and con dcnscr. all of usual or suitable type for use with'comnuin ha tcry circuits. ls hen the hook is up, that when it relicvcdof the weight oi. the receiver, the circuit through the transmitter andreceiver; and when the hook is down, the line-carcuit is completed.

for alternating current only, through the ringer and condenser. Sincethe circuits are the same for all the lines, I will refer to the linefrom station A only. This consists of conductors 1 and 2, extending fromthe substation to the central oiiice. At the substation the talkingcircuit is completed through the wires 3-l when the hook is up, and theringing circuit through the wires 5 (5 when the hook is down. Thesefigures are useful for the purpose of tracing the circuits only. Turningnow to Fig. 2, the line-wires 1 and 2 appear at the left hand side ofthe figure, terminating in contacts of the cutoff relays M, which arenormally detinergized, so that in each case the line-wire 2 is groundedat 7 and the llllQ-WlIO 1 extended through lineil to the line-relay M,and so to main battery B and ground. The armature, m, of each line-relayM is grounded at 9, and when attracted is adapted to close upon terminalcontacts of wires luiding to the tens and units relays of the primaryselector sets. I preferably divide all the incoming lines in an exchangeinto groups of sayone hundred each, and to each group I apportion afixed number of trunks leading to connective apparatus. In a small orcomparatively inactive exchange the percentage of these trunks may be aslow as five, and in busy exchanges it may be raised to ten or evenfifteen. I assume, however, that ten. per cent. of connective apparatuswill he sufiicient to care for the present system, hence I provide tentrunks for each one 100 hundred lines, and a complete set of tens andunits relays in a primary selector group for each trunk. The circuitsherein illusiratcd show six lines, which for convenience I will call No.500, 50]. and 502 (Fig. 2) 1.05 and 510, 511 and 512 (Fig. 3). Thesubscribers circuits of Fig. 1 will fit any of these, and in order tofully comprehend the connections of these lines and the arrangement ofthe tens and units relays. it is necessary to consider Figs. 2, 3 and44; together.

In 2 and 3 the subscribers extension lines are shown coming into theirinitial terminals on the tens relays. which are of the type shown inFigs. 9 and 10. Each of these relays carries the terminals of ten lines,and for each trunk there are ten of these relays, so that for 100 lines,provided with ten trunks. there will be 100 ton point relays, containing1,000 linedcrmi'nals; from which it appears that each line can bemultiplied ten. times, which it should be in order to obtain. access on(urcasion to every one of the ten trunks. The contacts on the ten pointrelays are arranged in duplicate pairs. That is, the incoming linesterminate each on one pair of springs, opposite which another pair ofsprings appears to which the line. is connected. when the relay isenergized, and from which a local circuit passes tered. At the top ofthe figure I have shown to the front contact springs of a particularunits relay or single point relay. For each group of ten tens relaysthere are ten units relays, or twenty relays in all for each trunk. .z-igroup of this kind constituting one primary selector or dummy trunkterminal for thirty lines, is shown in Fig. 8, apart from the otherfigures, so as to free the lines from their multiple connections. Inorder to make clear the Connection of a line coming into the exchange, Iwill first refer to this figure and then trace the-circuits through the.others.

lin Fig. 8, N, N, N are three relays of the type shown in Figs. 9 and1.0, having ten pairs of contacts each for the line circuits. Theserelays correspond to the relays shown in l i 2 and 3, correspondinglyletthe terminal ends of lines 500 to 529,'inclusire, connected to a pairof contacts, n a, such as shown in the niechanicalfigures 9 and 10. Forlines 500 to 509 these terminals are in the relay N. F or lines 510 to519 they are in the relay N. For lines 520 to they are in the relay NThus each relay contains line-terminals, a a, for ten lines. /Vhen anyone of the lines appro priated to a particular relay is calling, theelcctromag'net, n, of that relay becomes energizaed. This will beexplained in connection with the circuits of Figs. 1 and 2 farther on.For example, if any line from 500 to 509 originates'a call, the magnet,n, of the relay, N, will. become energized, and si-. niultaneouslyconnect all of the lines from. 50 to 509 onto the extensions to 19, inelusive. If, however, thecalling line. is in the group from 510 to 519,the magnet, n, of; the relay, N, will become energized, connecting allthat group onto the extensions 10 :"o la. inclusive. Similarlyflit thecalling no he in the third group, from 520 to 529, the magnet, a, of therelay N will be ener gixed. coilnccting that entire group onto theextrusions 10 to 19, inclusive. Thus extensious 10 to 19- are seen to becommon to all of the tens relays, and in fact each extension pairmultiplied to corresponding contacts in al of the tens relays. No. 1.0extension ;g'ocs the first pair of contacts, n, in each of the relays,l?l, N, N Exten l'fo. ll lllllllllplleflho the second pair r, contacts,a, a, in each of the relays, and so on with all the extensions up to No.1%

at thr lower edge of Fig. 8, I have shown ten units re ays, marked P toP, inclusive. These are the same as the relays in Fig. 4, similarlymarked. Each is a simple standard relay, of the type in common use, andpreferably of the same general type as that shown in Figs. 9 and 10,hereof, viz., that type in which the elcctromagiiet is mountedhorizmntally on a frame or rack, carrying the. contact'springsupon'it,and the whole l is inclosed Within a dust-proof shell. Each relay has anarmature, 19, adapted to be actuated by an electromagnet,p,- to closetogether the contacts, 32 p and 79 p". In the present instance, that isin the trunk group of each primary selector, all of the contacts, 7 p ofthe entire set of relays, P to P are connected together, forming a setof double parallel branches marked to 29, inclusive, which are really somany open bridges across the trunk circuit, 3lv a The outfit shown inFig. 8 is suilicient f0 30 lines and by its use any one of the lines,500 to 529, may connect itself to the trunk 30-3l, by merely closing itsline-circuit, and energizing the appropriate tens and units relays. Theenergizing circuits are not shown in Fig. 8, but will be described inconnection with Figs. 2, 3 and l. They comprise pa allel branches closedby the line-relay of each line when calling, one

branch going to the z'q'ipropriate tens relay,

and the other ranch going to the appropriate units relay, which thusbecame energized simultaneously and act in conjunction to connectthatparticular line and no other to the trunk. For example, suppose lineNo. 512 is calling, the subscriber having taken down his receiver fromthe hook, so as to close his line-circuit similar to the ones shown inFig. 1, and energized his line-relay, M shown in Fig. 3. This line-relaycloses two branches, one leading to the tens relay, N,iu F 8, and theother leading to the units relay, P which is the third in the set often. The actuation of the tensrelay, NT, connects all of the lines 510to'5l9 onto the extensions 10 to 19, inclusive; but it will. be observedthat these extensions are open everywhere else, hence no effect isproduced. by this action alone. The third units relay. I, however,connects the third extension 12 to the trunk 303l, through the branch22, and by following the circuits in Fig. 8 it will be found that'thisconnects the line 512 onto the trunk direct, whereupon the trunk relaysbecome energized, and further proceedings may be had. Only one line isthus connected to the trunk at a time, assuming of course that only one,tens relay and one unitsrelay of the same set be energizedsimultancously. It is true that the tens relay connects all of its linesonto the extensions; but all of these extensions are open except theparticular one whit-his closed onto the trunk by the particular unitsrelay energized. It is also true that the extension thus connected tothe trunk is multipled to theeorresponding pair of contacts in everyoneof the tens relays, but this produces no efifect, because all but one ofthe tens relays remain deenergized.

Before passingftfrom 8 it is necessary to call attention to thefact-that only three tens relays are there shown," accifinmodatingnecessary limitations of a Patent Office drawing, and it is to beunderstood that the same principles apply to any desired group up to ormore. It is most convenient 111 a scheme like this to make use of thedecimal system, using ten relays per trunk, ten lines per relay, and tentrunk multiples per line.

' For 100 lines there would be ten of the tens relays, N, N, N etc, .butstill only ten of .the units relays, and each of the extensions 10'to19, inclusive, instead of being multipled three tinies, would be'multipled ten times, into all the tens relays.

Turning 'now to Figs, 2, 3 and 1 we have here the same relays describedin connection with Fig. 8, but somewhat differently arranged. Only twotens relays and three units relays 01 each set or of each trunk areshown. I have assumed the numbers 51.0, 501, and 502 for the linesentering Fig. 2, and 510, 511 and 512 for the lines entering Fig. 3. Thefirst three lines being within the same tens digits ofeachv other goonto the same tens relays in each set. For the sake of convenience Ihave given the designating numerals of the relays coeflicients, and havemarked the three trunks in Figs. 4.-

I and 5 so as tobe readily followed. Thus in Fig. :4 all three of thelines come into the relay N, which is adapted to put them onto theextensions 10, 11, 12, etc, leadingto the units relays, P, P, P etc., inFig. 41. (I should here remark that the tens relays in Figs. 2 and 3 arenot shown with their full complements of springs, for tliesake ofsimplicity.) Each of-tlie lines 500, 501 and 502 not only terminates incontacts of the relay, N,-but is multipled to similar contacts in therelays 1N, 2N, etc. There would be one of these added for each trunk,that is appropriated to the group of lines. In the present case I onlyillustrate three trunks, so that each line need be multipled only threetimes.

In Fig. 3, the lines 510, 511 and 512 are connected to the tens relays,N, 1N- and 2N in the same manner as the lines in Fig 2,'each line beingmultipled three times so that each may have access to any one of thethree trunks. It will be understood 01 course that the relays, N, N, ofFigs. 2 and 3, and 'P, P, P, of Fig. 1, constitute one set, appropriatedto the trunk 3031, and hate precisely the same relation among themselvesand the same connections, as the set shown in Fig. 8. Similarly therelays 1N, 1N, 11, 1P, 1? all belong to one set, appropriated to thetrunk-line 180131. Similarly again, the relays 2N, 2N, 2P, 2F and 21?belong to one set, appropriated to the trunk-line -230231. Theextensions from the tens relays to the units are marked 10, 11,12 forthe first set, 110, 111, 'and 112 and 53 iass along the bottom of Fi 's.

for the second set, and 210, 211 and 212 for the third set. As these ofcourse bear a logical relation throughout, and follow the samearrangement as that in Fig. 8, it is thought no diiiiculty will beQXpOPlOIlCQd in comprehending the meaning of Figs. 2, 3 and I. If Fig. 8is understood, the description of the other figures may be put into onesentence. They show several. groups like Fig. 8, with the line-wiresmultipled to each group instead of terminating as in Fig. 8 in singlepairs of contacts.

The actual connection controlled by the relays N and P being thusunderstood, it is most important to explain the n'ieans by which Icontrol these relays. Referring to Fig.2,the linewircs 1 and 2 terminateas I have stated, in the contacts of the cut-oil relay M through whichthey are normally connected-to the line-relay M and ground. lVhenthesubscriber at ration A takes the telephone from the book, he closes hislinecircuit, .the linc-relay'M is energized, and the two branch circuits50 and 51 are immediately closed. The branch 50 passes in. multiple toone winding of each of the three tens relays, 1*, 1K and 2N, theserelays being double wound for the purpose of making them selt'lockingwhen attracted. Any one of these relays mightthus be energized by anyone of the three lines shown, but it is my purpose that only one of:them shall be so energized at once, and that no two lines shall be ableto energize the same relay at the same time. Hence, on the other side ofthese'relays I take away the circuibwircs, which were designatedgenerically by the numerals 5-1, 55 and 50, to three separatecontrolling means in the shape of specialrelays" associated with theswitch trunks.

Each of the firstnamcd relays has its lock ing coil open on one side,but adapted to be grounded by the relayitscl'l in pulling up; and on theother side of this second or locking winding it is connected through oneof the wires indicated by 57, 58, or 59, to controlling means similar tothose I have just mentioned and which will also be specified later. Thesecond branch from the line relay is marked 51 for line 502; 2 for line501; and for line 500.- In other words, eat-h of these lines has its ownunits wire, as will be apparent at once if Fig. 8 has been understood.The three wires, 51, 52, 0

4-1 and 3 and into 1, where they terminate in the first or operating,windings of the three relays, F, I" midi, also by multiples in thecorres nidiim windings of the relays, 1P, 1P. 1.. and 21, 2? and 21. Thethree relay long to the same set, have a common con; trol, their rcturnwires (of thesct 51) .n arked 51,51 and 54", passing to contacts I, 1and. 1, since they be-.

in a twenty-pair relay D". This relay controls the return wires of boththe tens an units relays of this set, twenty in all. I find it advisableto have a relay provided with separate terminal contacts for each of thewires 54., 5 B, etc., in each set 54, 55 or 56, because of certaincomplications which arise when battery is put on without any resistance, the working then being on a margin which is too narrow to becalled absolute. In other words, when the controlling relay for any sethas cut off the return wires from the actuating windings of the tens andunits relays, they are all separated from each other and as those of onetrunk only are closed together at any one time, the separation of therelays associated with the other trunks prevents the formation of anyparallel paths whena line calls.

Each of the units relays in Fig. 4 has a locking winding separated 'fromthe actuating winding and each locking winding terminates on one side ina contact normally open but adapted to be grounded when the relay isenergized. All the locking wind ings of the first set or group have acommon return, 61, passing onto the wire 57, which is the control wireof the locking windings on the tens relays,.N, N. This wire 57 passesinto Fig. 5 and is there carried to a pair of the trunk relays by whichit is controlled. The actuating windings of the units relays, 1P, IF,and 1P have return wires generically indicated by the numerals ($2, (andindividually as 62, 62*, etc.), passing to the contacts of the relay 1D(of Fig. 5) associated with the trunk 130-131. The lockingwindingsofthese. relays have a common return 63, which goes to the wire58, passing into Fig. 5 and there controlled by one of the trunk relaysin the same manner as in the first set. Similarly, the actuating andlocking windings respectively, of the units relays 2P, 2P and 2P havetheir return wires passing into Fig. 5 and there controlled by relaysassociated with the trunks It is thought the scheme will now be plain.

Suppose that one of the line-relays, as that of line No. 502, pulls up.It grounds the local circuits 50 and 51 and energizes which ever one ofthe ten relays, L 1N or 2N happens to be eligible, together with theappropriate units relay. This would be one of the three relays, P 11, or2P in Fig. The tens relay and units relay thus selectel having pulledup, their locking windi gs are grounded, and hence they are maintainedenergized through the locking common re turn wire as long as asubscriber keeps-his receiver olf the hook, being finally deprived ofcurrent when the subscriber hangs up, so that'the relays are thenrestored. I have thus shown, first, a single trunk group of idleconnector switch. wire 57 or 59 from the locking windings of primaryselector relays, andsecond three such groups, or at least portions ofthree groups, belonging to three several trunks, and having thesubscribers lines connected to them in multiple. I will now point outhow a calling line is permitted to select an idle trunk only, by workingidle relays only. For this purpose it is necessary that I should referbriefly to Fig. 5. This figure shows portions of a trunk circuit, eachof which commences on the left of the figure, which is supposed to bethe terminal point of attachment of the selective set shown in thepreceding figures and in Fig. 8.

The three trunks are marked respectively 30'-31, 130-13l and 230-231.Each of them is divided by condensers C so that the portions to theright of the condensers in the figure can be used for sending directcurrent out through the switches without interfering with the incomingcall end. I have designated the outgoing or switching end of the trunkas 30 ,31 etc. Across the incoming or answering end of each trunk isbridged a pair of relays D, D, 1D, 1D, or 2D, 2D, each with the mainbattery B between them. This battery is grounded as usual on itspositive bus, and when the primary selector set first puts a call on oneof the trinrks, as 30-31, its sleeve relay D will immediately pull up inseries with the cutoil relay of the calling line. The incoming end ofthe trunk, therefore, corresponds to the answering cord circuit of anordinary manual system, the primary selector set performing the samefunctions as the answering plug and jack; hence, the battery supply fortalking as well as for signaling over the ca ling line is drawn throughtwo relays l), D. 1) being the sleeve side relay, remains energized aslong as the primary selector set is on. The relay, D, on the other handresponds to the subscribers acts, being energized by current coming overthe subscribers line, and therefore controlled by his switeh-hook. Itwill be observed in the switching end of the three trunks shown in thisFig. 5, that in each instance there is a relay, E, but becomes energizedwhen the calling plug is inserted in a trunk jack leading to an I runthe common all the primary selector relays of each trunk toa backcontact on the relay F1 this contact being normally closed upon mainbattery B, These relays are all energized when the switching is done,but they serve nor mally to keep current on the locking wires, so thatwhen any set oi relays pulls up it will be enabled to lock instantly,even before the tip relay D of the trunk has pulled up. When this latterrelay becomes energized, it takes control of the locking wire in everywhich is normally deenergized,

point out how the actuating windings of the different. selective relaysets are rendered active one at a time. This is by means of the relaysD, D". In Fig. 5 it is assumed that the lowermost trunk is No. 1, thenext above is No. 2 and the uppermost trunk,

3031 is No. 3, in the order of their becoming busy. The instant a callcomes in and is put on the lower trunk, 230231, its sleeve relay 2D ispulled up and puts battery on the relay, 2D This latter relay isnormally deenergized, and the actuating windings of the various tens andunits relays belonging to its trunk are'therefore normally closed ontobattery through the wires 56, 56, 56", 56, 56 etc.; there being twentyrelays to the trunk and hence twenty wires for the actuating windings, lemploy a ten-pair relay of the type shown in Figs. 9 and 10, at thepoint, 2D". Of course the sprin 's on this relay may be arranged toeither open or close the respective circuits when the relay isenergized, as the case may be. The relay 2D or the first trunk must openthese circuits, Succeeding relays must leave them normally open and whenenergized must close them. In other words, as l have illustrated them inthe drawings, the first relay 2D is normally closed when. deenergizcd,but all the rest of the relays in the series, as 1D are normally openedwhen det nergized, so-that the relay selector of the first or lower-mosttrunk is in condition to get current at once and hence will take thefirst call. As soon as this call is placed on the trunk, the relay 2Dputs battery on the wire 14 leading to the armature of the relay 11) ofthe'next trunk, which normally completes the circuit of the relay lD Thelatter becoming energized immediately closes battery onto theactuatingwindings of the relay primary selector set of its trunk, whichthereupon. become sensitive and in condition to take-the next call; andso on to succeeding; trunks. I have shown only five contacts on each ofthe controlling re lays, for the sake of simplicity in illustration, butit will be understood that there may be as many as are required. Therelay D when energized closes the circuit of the signal lamp 0- throughthe normally closed contacts of the relay E The relay E is energized inseries with the resistance coil 1 when the plug P is inserted in thejack J. The energizing of this relay opens the circuit of andextinguishes the lamp 7*. The relay E when energized connectspneterminal of the lamp '1 to ground and when the relay D falls back theother terminal oi. this lamp is connected to battery causing it to glow,notifying the operator that the calling party has hung up his receiver.The wires 15 and l6 connected to the tip and sleeve of the plug 1 leadto a set of buttons which control impulses from a sending machine.

In Fig. 6, Q", Q, Q, Q Q, Q, Q, etc, are a set of'wheels mounted. on andturning with a common shaft, which may be driven. in any suitablemanner. The wheel Q), puts battery and ground alternately on the wire20, which for purposes of illustration. represents the metallic shaftconnection between the whecls. The wheel Q. is insulated from the shaftand is grounded and has an insulating spot in its periphery, andvcontrols by means of this spot the locking and. unlocking wires 30 and31, in a manner which will appear from the statement; of operation. Thewheels Q, Q Q, Q", Q, etc, are number wheels, the first one having onetooth, the second two teeth and so on up to ten teeth. (For simplicityof illustration only five wheels are shown). Around these wheels arethree sets of pens, connected to the three sets of keys K, K K. As thewheels revolve from the position. in which they are shown in the figure,they first make connection with the upper pens q, then with the pensthen with those of (7. The first set with their buttons or keys, K,transmit thetens'digit of any number, the next set transmit the unitsdigit, and the third set transmit the ringing; number for party-linowork. All this will appear more clearly from the statement of operation.

' The keys, K, K K are of the sorallcd self-latching selective ringingtype now in common use on manual switchboards, and employ theprincipleshown in the patent to Ham, No. 605,097 granted. June 7, M98.When any key is pressed down it pushes back the latch and releases theone that was previously down, then latching itself. Each set of keys hasa'common wire, this lor the sets K, K, being marked 32, these two beingjoined together and carried to a bnch contact of the relay R, while thator the set K is marked. 33 and carried to another hack contact of thesame relay, separately controlled. The numbers to be sent are set up bydepressing the keys, and thr-u {he sin-1- nal is started at thebeginning of a rolal ion of the shaft, when the first tooth ol eachwheel is about to strike its pen 1 by the relay, R being dciinergizcd,while the relay R remains energized. The lriclc of this is in thearrangement of the spring pens q. 1,

on the wheel Q. This wheel is roiuledivith the others in. the directionof the arrow, and its insulating spot passes first under the (jfi springpen 9, momentarily cutting ground oil of that and the wire 81, thenunder the pen 9, taking ground off of that.

It will be noted that the bank of keys is divided into three sets orrows, K, K and K respectively. The rows are each provided with thelatching device of Ham, cited, the rows being independent of each otherin this respect; thus one key and only one of each row will remaindepressed, the previously depressed key of each row being released bythe depression of anyother. In a bank or row of keys of this nature, akey is depressed through a travel carrying it beyond the locking point;upon release it returns a very short distance and remains locked thereuntil released by the depression of the next key used. I take advantageof this detail in the row of keys K in the fol lowing manner: The pairsof springs as 70* are to remain locked when the key is pressed, asdescribed later, but the triple springs in are springs requiring but amomentary contact to energize primarily the pair of lock ing relays R Tosecure the desired end, I so the relation of the springs is to the pushbutton. of the key that they are closed by the button when at its pointof farthest travel but are released by the slight return travel of thebutton before it is locked. The springs 7 2 however remain closed untilthe button is unlocked and fully released. V

In calling the number wanted which We will assume to be the operatorplugs into the calling jack. then presses down but ton No. 3 of the setK; No. 2 of the set, K

and No. 3 of the set K The buttons of the sets K and K have theirseveral individual wires connected to the pens on the several individualwheels Q, Q, etc, and the effect of pressing down the buttons asmentioned to connect the pen of the wheel Q through the springs 1 of thebutton l: to the Wire 32. wheel Q" connected throughthe springs M of:the button 71: to the wire33 and the spring 9" the wire The set ofbuttons K also have what i may call starting springs This set of buttonsbeing: the last, or ringing set, the number is ready for transmissionwhen any one of them depressed, hence any one of these buttons not only'iinishes setting up the number, but by closing the springs 7. putsground on the starting wires 3'7 and 3S. which pass to the two relays R,R res iievtively, and thence through the common return wire 89 tobattery B and ground. Both the relays pull up, and both look, thelocking circuit 01 the relay R being as follows: B, 35), R "1 30, 9 Qand ground. The locking (circuit of R is as At the same time the pen Q2of the 7 p of the wheel Q." is connected through the springs For thebutton 70 to follows: E, 39, R, r'", 31, g, Q, and ground. Having'thusset up the signal and put it in condition to be started at the beginningof a revolution of the" main shaft, and having also plugged into thenecessary hundreds group, the operators work is finished. She pays nofurther attention to the connection until the subscribers have completedtheir conversationand have hung up, whereupon the relay .Drcleases itsarmature, breaking the locking circuitoit' the relays of the pri- -maryselector; by the release of the primary selector relays, the connectionbetween the relay D'and the cut-off relay of the calling line isinterrupted, the relay D releases its armature, andthe lamp 7' lights tocall for disconnection. The operator then pulls the plug P.

The signal having been set up as described, the apparatus of Fig. 6 thenoperates as follows: The wheel, (#2, in revolving will bring theinsulating spot under the pen 9 at first, and might thereby cut oil therelay R prematurely, but this is provided for by making a branch lockingcircult 310 which is cont-rolled through a con tact of the armature 7"and a ground wire 36 of the starting relay it. Hence, as long as therelay R is energized, the relay It cannot be affected. Moreover, it willbe observed that the wires 32 and remain disconnected from the wires151(3 until. the relay RF energized, while therelay R is tle'energized.This condition is brought about wluen the insulating spot reaches thepen g. The relay R then lets go, and we have a continuous circuit fromwire 32 as follows: 32, *1", 31', r, 16, (in Fig. 5), and to trunk wireill. \Fe also have a circuit from wire 33' as follows: W 35, T 15, (Fig.and the other trunk wire 113. The insulating spot reaches the pen g justbefore the first tooth on each wheel reaches its pen 9'; hence soon asthe above desired condition is attained, the set of impulses which hasbeen determined by the key is of the set K comes from batter I over thewire to the wire 16 and so onto the wire 114: of thetrunk, through whichit passes into Fig. 7 to the relay R which. will be presently described,and which I shall call for conveniene the vertical relay. At the end ofthis group of impulses, the teeth on the wheels will have gotten aroundto the pens and so the non. group of impulses determined by the key ifwill pass from ground onto the wire 33 and so to the wire 15 and thetrunk Wire 113, through which they reach the relay ll in his. 7 whichwill also be presently described and which I shall for convenience callthe rotary relay. The names of these two relays are quite accurate inthis system, because the relay B does really produce a vertical motionof the switch the trunk wir, 11 1 and to the vertical relay R. Afterthis, the insulating spot on the wheel Q reaches the spring 9' andmomentarily cuts off the ground therefrom. Since the relay R is alreadydeenergized, this breaks the locking circuit of the relay 1 and it letsgo, disconnectingthe wires 15-1( -from the wires 31 and leaving theapparatus free for another operation.

Referring now to Fig. 7, I will briefly describe the switch operation.The switch spindle'controls a pair ofsprings s which it opens when it isdown in its normal position of disuse, for restoring purposes, as

. will presently appear. 3 is the release magnet of the switch, whichwhen energized removes the detent pawls "from the respective ratehets ofthe spindle, s, allowing the spindle to drop down and rotate back tozero, as fully described in the Patents 815,176 and 815,321, both oililarch 13, 1906, to Keith ct a l. This release magnet is under thecontrol of the relay R which in turn is controlled by the relays R and RIt is also under the control of the test relay R d3. is a ringingcontrol relay,,E is a trunk cut-off relay and R is a ringing relaycontrolled by the commutator X which conimen to the entire exchange. itis a slow acting relay, prei' n'ahly a solenoid, which connects the testrelay R, at the moment 01 eil ecting connection, as controlled by thefirst ringing impulse, and at the same time opens the generatorcirci'iit 14-O1 t1, while the proper current is being selected. 11 to R,inclusive, are selective relay." for enabling one or the other of theringing generators, (i, G", G and G, to be connected onto the ringingcontacts oi the ringing, relay, it, the particular generative beingditermined by the number of impulses received through the relay it whichoperates the relays it, it, etc, in succession, ca :h of them locking asit operates.

The o icration of this trunk scheme is as l follows: in selecting thenumber we have assumed 32* (the trunk itself corrcspomls to the hundredsnumber, if such there be) we have first three impulses from battery overthe wire 11% to the relay it, then two impulses from ground over thewire 11?) to the relay PM, and then three impulses from battery over theWllOlll to thi rclay R. The first three impulses coming over the wire11-icauses the relay ll to pull up three times, each time closing the'lollowing circuit; 13, 142, 143, 1 1-1, .9, 1&3, 1-16, 1 17, and groundto battery. The vertical magnet 8 steps the spindle s of the switch 11 3three steps, so that the wipers s stand opposite the third row ofcontacts. 'llwo-impulses then come over wire 1.13 ailecting the relay Rwhich pulls up twice, the first time closing the following circuit: B, 11-2, hf, 1 1-9, armature of R ,-a1-1natiire of R 151, to ground and tobattery. The relay R instantly pulls up, cutting oil the verticalmagnet, 8 and locking itseli by the following path: B, 1-1-2, it, 1*,152, 151 and ground back to battery. The vertical magnet s is thereforecut oil for the rest of the transmission. The rotary magnet 3, however,gets current each. time the relay R is energized, over the followingpath: B, 1&2, 14-3, 114-, a", armature of relay R 15%, 155 and groundback to battery. The rotary n'iaguet '3' turns the spindle 8 two steps,so that the wipers s rest on the second pair of contacts in the thirdrow, or No. 32. Three impulses now come over the wire 11%, causing therelay R again. to pull up three times. Each time it closes the followinglocal circuit: I), 1 12, R, 157, 1 1-6, 141-7, and grmmd hack tobattery. As a branch of this same circuit, the wire 1438 comes in frombattery wire 112, through the solenoid ll and goes to 157, 11H), 1-1-7and ground. At this point in the dcveloynncut of the connectionimmediately Following the closure or the contacts-of relay l? at thebeginning oi the first gcnci'ator-selectiou impulse, two things occursimultancmlsly:

(1) The solenoid R attracts its core, opening the wires 110 141 andclosing the switch 16?] whereby a test circuit is formed throughelements ll, 1-1-2, 1(32, 1, 16?. to upper s, which at this moment isresting 'in contact with the line selected through the" agency ofvertical and rotary magnets a 8"," it the line be busy because it iscalling, then a circuit will exist from upper wiper 3 through the linemultiples to the tip side of the other trunk used in answering, and,thrcugh the relay 1) of that trunk to ground; while if the line is busybecause it has previously been called then the test circuit willcontinue through the line multiples to the wiper s of the other switchused, in calling the line, thence through the other trunking equipmentfollowing a path corresponding to contact of ll, contact oi It,conductor 11 and winding of lit to ground; in either case the test relayR will be energized and in turn will energize the release magnet s. it,however, the selected line with which the test wiper rests in contact isnot busy, no circuit will exist from lhat lest wiper to ground and thetest relay it will not be energized;-

' a branch path for the conductor H33 exists through the talkingconductor of the lruult to lhc left hand contact of relay it and thenceto an armature contact of relay R where it terminates open, butsubsequent to the cnergization of relay It as about to be describedfthisbranch path passes to the inner contact of the left hand armature ofthat relay and thence over the conductor 141 to the right hand switch ofthe solenoid .R which during the test period is open, and thus testrelay It has its circuit open at all points and the design of. thedevice as a Whole is that no OHGI'g'lZZttlUIl of that relay may resultwhen the line selected is in a condition of disuse and subject to use inthe connection now being established.

(2) The relay It is energized over the path B, 142, R 157, 14:6, 147 andground. By the closure of the left hand armature of relay t circuit isformed through elements B, 1.42, 156, armature of R, 160, winding of R161, switch 8 and ground, energizing relay E which leeks itselfenergized over the circuit B, 142, 1-1-3, armature and inner contact ofrelay it", winding of relay it, 161, s 'and ground. This energization oftrunkconnecting relay It connects the conductors 1li-113 ot' the trunhthrough to theoutta' contacts oit't-he ringing relay R and through tothe wipers 5". This furnishes a path through test relay It as follows:B, 142, 162, R 163, talking conductor to left hand armature of R backcontact and talking conductor to armature of energized relay lt",conductor 114, winding of relay It and ground; how= ever, this circuitis adapted to be opened by the attraction oijithe arm: tures of relay itand it is the function of the connector switch that the o )enin of thiscircuit at It shall succeed its closing at 1t b a time limit so smallthat restoration of the connector switch is not pern'iitted. it will henoted in the study of this time element that the test relay lt mustattain the degree of mag netization. rri uired to attract iisarn'iutnre, must swing its armature through its full travel. to closeits contact, "and that subsequently to the closure of the contact ol' Rthe release magnet a" must reach its required degree of magnetizationand must overcome the inertia oi its armature and more it through somedefinite arc hetero release of the switch will be ellected; this seriesol' neev Marily consecut ve operations limits the duration of theiuomenta l'alse test here considered. The commutator X is carried. uponthe shaft which =arrics the number wheels and commutator devices: Q, Q,Q.

(a etc, and the commutator X is adjusted angularly with respect to thosewheels so tlr" the conducting portion of X. isin clertriral warm-mienwith its brush at the time that thrern ririzaation oi relay lt' occurs.it is seen the: to

contacts oi" relay it. by which current flow thrinre'h test relay it waspermitted, rur

rent flow also was sinuutruieousiy provided for thron h the )Hlll 13. H2H, \UWUHT of o l a a cs y It, contact and armature of r, 168, r, 101

and ground. Thus current begins to flow through the winding of relay Rat the same instantthat current begins to How through the Windingofrelay R and, assuming equal speed in the operation of armatures, relayIt will have moved its armature and will have broken its back contact,thereby cutting off current from relay B in ample time to prevent therestoration of the switch by operation of release magnet s, the break atthe armature of R probably occurring in time to prevent anycontact whatever at the armature of relay R Thus a test condition is maintained withthe test wiper a. isolated from the winding of relay H. by the break atthe armature of relay 1t, and the design andadjustment of the commutatorX shall be such that the relay it is held energized through the maximumperiod occupied by generator-selection impulses and until the opening ofthe circuit of the test relay 1% by the opening of the switch 162 uponrelease of the armature of the solenoid R". The armature of the solenoidR issluggish and does not open the switch 162 between thegeneratorselection impulses, so that the test circuit here described ismaintained contimiously during the period of generator-selection.

Leaving the various parts of apparatus in the condition now considered,we will follow the action of the apparatus in response to thegenorator-selection impulses. In the instance assumed, ice station No. 3is to be called three battery impulses will be received over the wirellatoperating the armature of the relay it successively three times,which in turn acts over the path 14:7, lit 157 it, etc, to operate thearmatures of relay it in SIICCUSSlOI]. three times; the armature rthrough its front and back contacts eti'ects the selection. of thedesired ringing generator as follows: Upon attraction of r the firstgeneratouselection inipulse, it makes electrical connection with itsinner contact, but inasmuch as the Wire 16d is open at the armature ofrelay R no complete circuit is closed. Upon the release of the armaturer at cessation of the first gen erator-selection 'impuise, circuit isclosed through elements I), 1 4-2, 113, contact of R 5, H30. 1-, 16?,contact of 1:1 winding of R and ground. energizing relay R which locksover the circuits B, 1.42, 1-1-3, contact of 11", nee. 1 W. armature andcontact ol it, windingoi R and grrnind. ll but one gelierator-selhctiiinimpulse were received, the gg enerator (i would remain in .ronuectionnith conductor 14o ready for re that by the closing of the 1 connectionthrough conductor Il-ll to the ringing relay 11". At the l'ieginnlng oithe second generator-seleetion impulse, relay l? is chore" .ed andarmature r is altrartwl,

(losing r nit through elements B, 14.2, 1'10, contact of R 160. r", 164,closed contact .contact of R 160, 169, armature contact and winding of RUpon the cessation of the second generator-selection impulse, thearmature 1' is released, closing circuit over B, 142, 1&3, contact of l160, T, 165,

closed contact. of lower armature of energized relay R back contact oflower armature of unenergized relay R", winding of relay R and ground,energizing relay R which then locks itself through its own contact bycurrent received over conductor 169 toground as in the case of relays Rand R. If no more generator-sclection impulses were received, theeil'ect of the two impulses thus far followed would be to leavegenerator Gr connected to cmuluctor 140 through contact of energizedrelay R, that being the proper generator for ringing the secondstationon a party line. At the beginning of the third and lastgenerator-selection impulse, the armature r is again attracted, closingcircuit over elements B, 14-2, 143, contact of R 160, 1- 164-, closedcontact of energized relay R closed inner contact of energized relay Rclosed outer contact of unenergized relay R winding of relay It andground, energizing relay R, which then locks itself by currentthrough'its own contact. and winding over conductor 169 to ground. Uponthe cessation of the third and last generator-selection impulse, thearmature r is released, closing circuit through elements B, 142, 14-3,con

tact of R 160, W 165, closed inner contacts of energized relays R and Rclosed outer contact of uncnergized relay R Winding of relayR andground, energizing relay R which then locks itself by current throughits own armature contact and winding from conductor 169 to ground. Thisleaves relays R and 1t" energized and leaves relays R unenergized, thuseffecting the connection of generator G to the conductor 140, and as thegenerator-selection impulses now cease, solenoid R releases itsarmature, opening the circuit of the test relay R and closing thecircuit between conductors 140-141, thus connecting the lected generatorGr over conductor 1-11 to the inner contact of the left hand armature ofringing relay l1 and thus through the upper wiper s and to the lineconductor of the selected line to ring the third station upon the partyline selected. The ringing will continue until the insulated portion oithe commutator X passes under the brush of that commutator when thecircuit of the Winding of relay R will be interrupted and by release ofthat relays armature the circuit from the wipers s will be removed fromthe generator and carried to relays R and the relay R.

It respectively. The line selected will be subjected alternately toperiods of ringing when the relay tis energized and to periods ofnon-ringing when the relay R is deenergized. Upon the answering of thecalled sub-station, or of any sub-station upon that party line, during aperiod of non-ringing, current immediately will ilow through elements B,142, winding of R 113, lower a, line conductor, substation bridge,return line conductor, upper s, 114-, winding of R and'earth, energizingR and attracting its armatures.

By the operation of the left hand armature of R, circuit is closedthrough elements B. 142, left hand armature and inner contact of R,winding of R 15 1;, contact and left hand armature oi R 155 and ground,energizing lt which then locks over the circuit 13, 1 12, right handarmature and contact oi? R to winding of R 1534-. contact and armatureoi R 155 and ground. By cncrgization of relay R ground is taken oil oi?wire 152 so that ringing relay R may not again be energized. Also by theenergization and locking of R the relay R is rel :ased and remainsreleased throughout the remainder of the connection. This is thecondition of conversation and continues until the hanging up of thetelephone and the breaking oi the substation bridge upon the rallcdline. Upon the hanging up of the telephone and the breaking of thesubstation. bridge upon the called line, disconucctimi of the switch iseifccted as follows: Circuit is interrupted over the return wire oi theline and through relay R to ground, releasing the armatures ofrelay R,but current continues through elements 1%, 142, winding oi R 113, lowerwiper s, and the sleeve side of the connected line and the winding o'iiits eut-oii' relay M to ground, maintaining the energization of Thiswill be apparent from an cxan'iination of Fig. 7 in connection with theline circuits in Fig. 2. The circuit from R to lit" is closed throughthe line sleeve multiple and the wiper s. liy the release of the lcithand armature oi relay ll a. release relay circuit is establishedthrough elements B, 142, left hand armature and outer Contact ofdei'nlergized relay .li, winding of release relay it, inner contact andarmature r of relay R 151. and ground, energizing release relay l t"which, by closing its contact, energizes release magnet s. which ,ci-129 feels immediate restoration oi all parts of the switch to the normalposition of disuse.

A consideration of test conditions during the process oi the connectionis desirable. When the test wiper or upper wiper 3 connects with thetest conductor of the line, no

action is taken either to test for busy or to place a busy test upon theline until the wheels Q, Q Q3, etc., have in due course tor-sclectionimpulses the test relay is taken off and the ringing generator issubstituted. From this time a'busy test guard condition is placed-uponthe test conductor of the selected line, being alternately the potentialof the selected ringing generator when the relay It is energized, whichis sutlicient to energize any relay R which may test the line during theinterval of ringing, and between the intervals of ringing the busy testconsists of the ground circuit throng 1 the relay R tested for busy bysome other connector attempting a connection with it and during theinterval of decnergization of ringing relay l a current will flow fromthe c0nnec tor thentesting tothe test conductor of the line, thencethrough the test wiper of the connector at l 3 l'iolding the line, andthrough back contact of relay it, front contact of R 114, and winding ofR to ground. This current will be of suliicient strength to energize thetest relay 1 11 of the distantconnector attempting to take the linebeing held, and this will eli'ect disconnection of that connector but itwill not be of suilicient strength to energize the relay Itii'iasniuchas by the encrgization and subsequent deih'icrg ration ofthat relay, the said testing current would also restore the holdingconnector of l ig. 3 to its normal condition of idleness. The relay l)in Fig. 5 falls back when the calling party hangs up his receiver thusopening the lo( hi1u wire 5T allowing the primary selector outlit tobecome di connected. The relay l) falling back closes the circuit of thelamp 1' notifying the operator that the parties are through talking andshe thereupon witlulraws the plug from the trunk jack.

I have thus described my invention 'in one specifi form for the purposeoi rendering it clearly com n'eliensible, but it is to be under stoodthat l do not limit myscll to the spewith form or arrangementdeseribeiil. 1 may vary the methods and n'iattcrs described in many wayswithout; departing from the spirit of the invention. 1 wish particularlyto call attention to the fact that there are certain features of theinvention which should not be limited to use merely in combination withothers. ll'hus, those portions oi? the invention shown in l igs. l toinclusive.

arc coi'nplctc, and the connecting jacks .l in r .r ig. 5 may well bethe multiple jacks oil: linc :ircuits, omitting the autcmratic switchesenti In such case the apparatus in l ig. 6 "could be superfluous, andthe cord circuit would contain the ordinary o 'icrator s listen- If theline thus connected with the 'ing and ringing key. The same may be saidas to completeness of that part of the invention embraced in Figs. 5 to7 inclusive, the incoming trunk ends being then taken as lines merely.All minor changes and adaptations; as Well as sub-combinations, I Wishto include in the scope of my claims.

In the claims hereinafter I shall refer to y B switches to indicateswitching mechanism which is definitely directed or driven to select aparticular line. The letter B is used as a convenient designation forthis type of switch because it is one of the algebraic symbols for knownquantities.

Having thus described my invention what I claim and desire to secure byLetters Patcut is:

1. In a telephone exchange system, a plurality of line circuits to beinterconnected, a plurality of terminal plugs less in number than thenumber of lines, and groups of relays associated with the respectiveplugs, each group common to a plurality of lines and containing terminalcontacts thereof-for connecting any line when calling to an idleterminal plug, together with automatic switching apyiiaratus containingmultiple terminals of the lines, and jacks forming terminals fortheswitch circuits, adapted to rece ve the plugs, whereby calls made overthe lines will automatically distribute themselves upon the plugs, andthe plug circuits may be trunked to automatic switches for the purposeof completing the connections desired.

lira telephone exchange system, a plurality of line circuits,a'plurality of terminal plugs, groups of relays common. to said lines,one group associated with each plug, for a utoinatically connecting acalling line to an idle plug, a signal associated with each plug andbecoming active when a calling line is connected thereto, and automaticswitches cooperating with said plugs to complete the connectionsdesired.

3. In a. telephone exchange system, a plurality of lines to beinterconnected, and connective apparatus therefor comprising thetollowii-ig lllfniji'llllltilll'illlillQS; terminal plugs, primaryselector switching relays in decimally arranged groups containing lineter minals, one group associated with. each plug, for connceti thecalling lines with idle plugs :uitoinatic switches and jack terminalstlmrcior, together with manually operated controlling apparatus for theswitches.

4-. ln. av telephone exchange system, a. plurality ol. lines to beintel-connected, and conncrtirc apparatus therefor comprising thefollowing instrmnentalities; terminal plugs, primary selector switchingrelays in decimally arranged groups containing line teriniuals, onegroup associated with each plug, for connecting the calling lines withidle pl ngs, automatic switches and jack terminals

